Applying an absorber technique, the experimental shape and width of a parametric x-radiation line has been determined. The 9 keV radiation was produced by bombarding a diamond crystal of 55 &mgr;m thickness with electrons of 6.8 MeV. The variance of the spectral line distribution was found to depend on the tilt angle of the crystal and to have a magnitude of &sgr;=51 eV. Simulations based on a Monte Carlo method exhibit that the observed variance is mainly influenced by multiple scattering of electrons passing through the crystal (≈43 eV) and the finite detector opening (≈18 eV), leaving for the intrinsic linewidth a value of the order of 1 eV. The spectral density of the line was found to beJ≈10−7photons/(electron×sr×eV). ©1997 American Institute of Physics.